1. Field of the Invention
The present invention is related to an axle driving apparatus having a housing enclosing an integrated hydrostatic transmission (HST) and a driven axle.
2. Related Art
Conventionally, an integrated hydrostatic transaxle comprises an HST (a hydraulic pump and a hydraulic motor), and axles driven by the HST which are housed within a housing. An output shaft of the hydraulic motor and the axles are operably connected for varying the rotational speed of the power generated by an engine to thereby drive the axles.
The hydraulic pump and hydraulic motor of the HST are conventionally disposed entirely forwardly or rearwardly of the axles. Such structure is disclosed in International Patent Application No. PCT/US95/04097 and in U.S. Pat. Nos. 4,914,907; 4,932,209; and 259,194.
The conventional hydraulic pump and hydraulic motor are disposed forwardly or rearwardly with respect to the axles, whereby the center section of the housing has a large width and/or length to accommodate the hydraulic pump and hydraulic motor. Furthermore, a ring gear of a differential disposed perpendicular to the axles, necessitates a longitudinally and vertically enlarged differential housing portion for enclosing therein the ring gear, thereby wasting space rendering it difficult to form a more compact apparatus.